Published patent application WO2009/150574A1 discloses a lamp unit which emits different wavelength spectra in different directions. The lamp unit comprises two light sources which each emit light of a different wavelength spectrum. The lamp unit comprises different optical means to direct the light of the different wavelength spectra in different directions. An embodiment relates to a retrofit light bulb which comprises in the middle of the light bulb a nontransparent separator on which a first light emitter is applied which emits light to the ambient through a first part of the light bulb. In the base of the light bulb is manufactured a second light emitter which emits light to a second part of the light bulb and to the nontransparent, but reflecting, separator. The first light emitter emits another color of light than the second light emitter. Consequently, through different parts of the light bulb light of different color wavelength spectra are emitted into the ambient of the light bulb. Another embodiment of the cited patent application relates to the placement of different light emitters on different sides a nontransparent support structure which is placed in a retrofit lamp such that the light emitters emit light of different colors into opposite directions. Other embodiments relate to using reflectors or light guiding structures which influence the light emission direction of light of different colors which are emitted by different light emitters.
The embodiments of the cited patent application are relatively complex, because they require, for example, a complex wiring pattern within the light bulb, and require special structures to which the light emitters are coupled. Further, the lamp units comprise at least two light emitters which each emit a different color. Thus, the lamp units of the cited patent application are relatively complex and as a consequence relatively expensive.